The present disclosure relates generally to heating, ventilating, air conditioning and refrigeration (HVAC&R) systems and more particularly to heat pump systems with multiple operating modes.
Many applications exist for HVAC&R systems. For example, residential, light commercial, commercial and industrial systems are used to control temperatures and air quality in residences and buildings. These systems generally operate by implementing a thermal cycle in which fluids are heated and cooled to provide the desired temperature in a controlled space, typically the inside of a residence or building. Generally, HVAC&R systems operate by circulating a fluid, such as refrigerant, through a closed loop between a heat exchanger where the fluid is evaporated to absorb heat and a heat exchanger where the fluid condenses to release heat. The fluid flowing within the closed loop is generally formulated to undergo phase changes within the normal operating temperatures and pressures of the system so that considerable quantities of heat can be exchanged by virtue of the latent heat of vaporization of the fluid. Certain HVAC&R systems are designed for specific applications, such as heating alone or cooling alone. Other systems, such as water-to-water heat pumps and reversing air source heat pumps are capable of operating in multiple modes to provide the desired heating, cooling, or other applications. It is now recognized that there is a need for improved HVAC&R systems that provide a variety of heating, cooling, chiller, and heat pump operations.